Product analysis - Pharmaceutical Biotechnology: Concepts and Aapplications - page 201

7.6.6 Miscellaneouscontaminants
In addition to those already discussed, biopharmaceutical products may harbour other contami-
nants, some of which may be intentionally added to the product stream during the initial stages of
downstream processing. Examples could include buffer components, precipitants (ethanol or other
solvents, salts, etc.), proteolytic inhibitors, glycerol, anti-foam agents, etc. In addition to these,
other contaminants may enter the product during downstream processing in a less controlled way.
Examples could include metal ions leached from product-holding tanks/pipework, or breakdown
products leaking from chromatographic media. The fi nal product containers must also be chosen
carefully. They must be chemically inert and be of suitable quality to eliminate the possibility of
leaching of any substance from the container during product storage. For this reason, high-quality
glass vials are often used.
In some instances it may be necessary to demonstrate that all traces of specifi c contaminants
have been removed prior to fi nal product fi lling. This would be true, for example, of many proteo-
lytic inhibitors added during the initial stages of downstream processing to prevent proteolysis by
endogenous proteases. Some such inhibitors may be inherently toxic, and many could (inappropri-
ately) inhibit endogenous proteases of the recipient patient.
Demonstration of absence from the product of breakdown products from chromatographic
columns may be necessary in certain instances. This is particularly true with regard to some
affinity chromatography columns. Various chemical-coupling methods may be used to at-
tach affinity ligands to the chromatographic support material. Some such procedures entail
the use of toxic reagents, which, if not entirely removed after coupling, could leach into the
product. In some cases ligands can also subsequently leach from the columns, particularly
after sustained usage or overvigorous sanitation procedures. Improvements in the chemical
stability of modern chromatographic media, however, have reduced such difficulties, and
most manufacturers have carried out extensive validation studies regarding the stability of
their product.
Sophisticated analytical methodologies facilitate detection of vanishingly low levels of many
contaminants in biopharmaceutical preparations. The possibility exists, however, that uncharac-
terized contaminants may persist, remaining undetected in the fi nal product. As an additional
safety measure, fi nished products are often subjected to 'abnormal toxicity' or 'general safety'
tests. Standardized protocols for such tests are outlined in various international pharmacopoeias.
These normally entail parenteral administration of the product to at least fi ve healthy mice. The
animals are placed under observation for 48 h and should exhibit no ill effects (other than ex-
pected symptoms). The death or illness of one or more animals signals a requirement for further
investigation, usually using a larger number of animals. Such toxicity testing represents a safety
net, designed to expose any unexpected activities in the product that could compromise the health
of the recipient.
7.6.7 Validationstudies
Validation can be defi ned as 'the act of proving that any procedure, process, equipment, material,
activity or system leads to the expected results'. Routine and adequate validation studies form a